The present invention relates to a method of molding a glass body which does not necessarily require grinding or polishing after molding. A glass molded body is prepared by transferring optical mirror surfaces of a mold assembly to surfaces of the glass body and can be used as an aspheric glass lens as well as a spherical glass lens.
A conventional method of molding a glass body is known wherein a special material is used for a main body of a mold assembly and surfaces of the molded body, the molded surfaces are constituted by optical mirror surfaces which do not require grinding or polishing after molding, and molding is performed in a non-oxidizing atmosphere.
A method of molding a glass body, as described in U.S. Pat. No. 3,833,347 includes steps (a) to (h): (a) glass mass is placed in a mold assembly; (b) a chamber surrounding the mold assembly is evacuated and a non-oxidizing gas is introduced in the chamber; (c) the temperature of the mold assembly is increased to about a glass transformation temperature (the temperature corresponding to a viscosity of 10.sup.7.65 poise) and is kept at this temperature for 1 to 5 minutes; (d) the mold assembly is pressed to mold a glass body; (e) the load state is maintained while the molded glass body is not deformed, and the temperature of the mold assembly is decreased below the glass transformation temperature; (f) the load is removed; (g) the temperature of the mold assembly is further decreased to about 300.degree. C. so as to prevent the oxidation of the mold assembly; and (h) the mold assembly is opened to remove the resultant glass lens.
According to the method described in U.S. Pat. No. 3,833,347, the temperature of the mold assembly is changed from the glass transformation temperature when heated to about 300.degree. C. when cooled by several hundreds of degrees centigrade. If an identical mold assembly is used to continuously manufacture glass lenses, a molding cycle time required for manufacturing one glass lens is greatly prolonged. In addition, heat efficiency is also degraded. Further, since the mold assembly is in direct contact with and heated by the glass body for a long period of time, the inner surfaces of the mold assembly are roughened to shorten the service life thereof.